Buyyounouski analyzed a database of 2,000 men who had radiation treatment for prostate cancer between 1989 and 2006. Aspirin users were less likely to have a recurrence, as measured by rising prostate-specific antigen (PSA) levels.
Ten years after treatment, 31 percent of the 761 men who took aspirin during or after radiation had developed a recurrence compared with 39 percent of nonaspirin users. The aspirin users also were 2 percent more likely to survive the disease after 10 years, although that finding was not quite statistically significant. Buyyounouski said the survival difference might widen with longer follow-up.
Does this mean that people should take aspirin to prevent cancer or slow it down? Buyyounouski says no, and officials from the National Cancer Institute and the American Cancer Society agree.
What his study may mean, Buyyounouski said, is that "if you're taking aspirin already and you have prostate cancer, you may get double duty out of it."
The cardiovascular benefits of taking aspirin after a heart attack or stroke are well-established, but its impact on cancer is much murkier, said Eric Jacobs, strategic director of pharmacoepidemiology for the cancer society. He returned Tuesday from a trip to London to discuss an international consensus statement on aspirin and cancer. Those who attended will now try to calculate the risks and benefits of aspirin for different cancers.
Even a baby aspirin a day can lead to fatal stomach bleeding, Jacobs said. Complications are most common in the elderly, the group also most likely to suffer from prostate cancer.
The cancer society does not currently recommend taking aspirin for cancer, he said.
Jacobs said the new Fox Chase study should be "interpreted cautiously because this is an observational study, not a randomized trial."
Mounting the kind of large randomized trial of aspirin for cancer that researchers want won't be easy. Because aspirin is already cheap and easy to get, the pharmaceutical industry is unlikely to fund such a trial. That leaves the government.
Leslie Ford, associate director of clinical research in the NCI's cancer-prevention division, said a cancer-prevention trial likely would take 10 years. "It is a topic for discussion," she said, but NCI wants to have a better understanding of why aspirin might affect cancer and who is at greatest risk for side effects before embarking on such an ambitious project.
Aspirin has a long history. Hippocrates, the famed Greek physician, reputedly used the bark and leaves of the willow tree in 400 B.C. to relieve pain. In 1897, a chemist at Bayer & Co. synthesized a stable form of the active ingredient: acetylsalicylic acid. Aspirin became available without a prescription in 1915.
Because of its broad effects, Ford said, "aspirin is probably the most fascinating over-the-counter drug that there is." However, she added, many think it could not get FDA approval now because of its side effects.
Buyyounouski said it was not clear why aspirin might affect cancer, but there is evidence that its anti-inflammatory properties might play a role. It may also encourage apoptosis, or the programmed death of cancer cells.
Timothy Rebbeck, associate director for population science at the University of Pennsylvania's Abramson Cancer Center, said the idea that aspirin could fight cancer was "plausible and interesting" given the growing focus on inflammation and cancer. But, he said, it's "not completely clear" that aspirin affects any form of cancer.
Experts said the evidence was strongest for colorectal cancer. "There's now very strong evidence that long-term daily aspirin does lower the risk of colorectal cancer and probably esophageal cancer as well," the cancer society's Jacobs said. "There is much less conclusive evidence . . . about certain other cancers, for example stomach cancer and lung cancer." Studies have been mixed, he said, for breast and prostate cancer.
Contact staff writer Stacey Burling at 215-854-4944 or firstname.lastname@example.org.